Natural gas detection pipe analysis traceability calibration device and method

Abstract

The invention discloses a device and a method for analyzing, tracing and calibrating a natural gas detection pipe. The method comprises the following steps: (1) mixing a quantitative detection pipe indicator which can be subjected to color change reaction with a component to be detected with a carrier; (2) the carrier is divided into n parts, n detection tubes are filled with the carrier, the indicator in each detection tube is m / n (mol), the stoichiometric coefficient of the indicator of a to-be-detected component is k, and the to-be-detected component consumed by full and complete reaction with the indicator is km / n (mol); (3) determining the ratio r of the color change length in the detection tube to the total filling length of the detection tube carrier, wherein the molar weight of the corresponding calibration target component to be detected is rkm / n (mol); and (4) measuring the natural gas sample size v (L), and detecting the concentration rkm / nv (mol / L) of the component to be measured. According to the invention, a mode of performing stoichiometry on the indicator which is subjected to color change reaction with the to-be-detected component is adopted, and calibration by adopting standard gas is not needed during measurement, so that the problems that the traceability uncertainty is high when the standard gas is adopted for calibration and the accuracy is poor when a detection tube is influenced by temperature, pressure and manual operation can be avoided.

Description

Technical Field

[0001] This invention relates to the field of natural gas sampling and analysis technology, and more specifically, to a natural gas detection tube analysis and traceability calibration device and method. Background Technology

[0002] Gas detection tube technology, also known as direct-reading detection tube, is filled with a silica or alumina carrier with a detection reagent attached. The outer surface of the glass tube is printed with a scale indicating the gas concentration. When the gas to be tested passes through the carrier with the detection reagent attached, it will react chemically with the reagent, causing a color change. By observing the length of the color-changing layer and reading the scale, the gas concentration can be determined instantly. It is characterized by its simplicity, speed, and low cost.

[0003] Existing gas detection tubes need to be calibrated before leaving the factory to verify the accuracy of their concentration detection. Therefore, standard gases of known concentrations of the analyte are usually used for calibration by passing them through the detection tube. However, due to the influence of factors such as temperature, pressure and human operation during calibration, the measurement results may be inaccurate when the detection tube is used in the field due to factors such as temperature, pressure and operation. Moreover, the uncertainty caused by the concentration of the standard gas itself must also be considered when using standard gases for calibration.

[0004] Furthermore, existing gas detection tube technology suffers from several drawbacks when performing high-pressure natural gas testing. Because the detection tubes cannot withstand the high pressure, the gas source must be removed for depressurization before sample injection. Inconsistent operation between different personnel and even repeated measurements by the same person are difficult to maintain. Environmental factors such as temperature and atmospheric pressure also affect the sample volume, leading to significant measurement uncertainty. Additionally, a large inner diameter of the detection tube results in a wide and blurred color-changing interface on the indicator carrier, while insufficient absorption by the injected sample and a short color-changing length also affect measurement accuracy. Conversely, a small inner diameter makes the tube fragile and prone to breakage. Moreover, the scale lines on the detection tube may overlap with the color-changing interface, resulting in an unclear interface and inaccurate readings. Therefore, accurate reading of the detection tube scale is impossible, leading to significant errors, low measurement accuracy, and an uncertainty of approximately 25%, making it suitable only for coarse measurements.

[0005] In view of the above, this application is hereby submitted. Summary of the Invention

[0006] The existing technology has the problem that the calibration of the detection tube using standard gas is affected by factors such as temperature, pressure and manual operation, which can lead to inaccurate measurement results when the detection tube is used in the field. Moreover, the uncertainty caused by the concentration of the standard gas itself must be considered when using standard gas for calibration. The present invention provides a natural gas detection tube analysis traceability calibration device and method, which adopts a chemical metric method using an indicator that changes color with the analyte, and uses stable pressure and flow injection and color change identification associated flow measurement technology to calibrate and trace the detection tube. The detection tube has high detection accuracy, and the measurement does not require the use of standard gas for calibration, which can avoid the large uncertainty of standard gas calibration for traceability, as well as the poor accuracy of existing detection tube calibration due to the influence of factors such as temperature, pressure and manual operation.

[0007] This invention is achieved through the following technical solution:

[0008] In a first aspect, the present invention provides a method for calibrating and tracing the source of natural gas detection pipes, comprising the following steps:

[0009] (1) Mix the quantitative m (mol) detection tube indicator that can react with the target analyte in natural gas with the carrier;

[0010] (2) Divide the carrier containing the indicator into n equal parts and fill them into n detection tubes of the same size. The indicator in each detection tube is m / n (mol), the stoichiometric coefficient of the indicator of the target component in the natural gas is k, and the amount of the target component in the natural gas consumed by the complete reaction with the indicator is km / n (mol).

[0011] (3) When using the analytical tracing calibration device to determine the concentration of the target analyte in natural gas, the ratio r of the discoloration length in the detection tube to the total length of the carrier filling the detection tube corresponds to the molar amount of the target analyte, which is rkm / n(mol).

[0012] (4) By measuring the natural gas injection volume v (L), the concentration of the component to be tested rkm / nv (mol / L) can be detected, thus realizing the calibration and traceability of the detection tube.

[0013] Secondly, the present invention provides a natural gas detection tube analysis and traceability calibration device for implementing the above-mentioned calibration method.

[0014] Includes a pressure testing tube, a color sensor, and a flow meter;

[0015] The pressure-resistant detection tube body includes a transparent pressure-resistant tube and a detection tube coaxially installed inside the transparent pressure-resistant tube. There is a gap between the outer wall of the detection tube and the inner wall of the transparent pressure-resistant tube to form a pressure-resistant cavity. The detection tube is filled with an indicator carrier of the target component to be tested in natural gas.

[0016] A color sensor is provided on the external indicator carrier section of the pressure resistance detection tube; the color sensor is electrically connected to the flow meter, which is located at the end outlet of the pressure resistance detection tube.

[0017] In one specific embodiment, the system further includes a sample injection system, which includes a three-way valve. One end of the three-way valve is used to connect to a sample gas source; the second end is used to connect to the front end of a detection tube through a sample injection pipeline; and the third end is connected between the end of the pressure-resistant detection tube and a flow meter through a bypass pipeline, and is connected to the pressure-resistant cavity.

[0018] A first vent valve is installed on the sample inlet line;

[0019] The bypass pipeline is equipped with a second vent valve and a shut-off valve.

[0020] In one specific embodiment, a pressure regulating device is also included, which includes a pressure reducing valve connected between the end of the pressure-resistant detection tube and the flow meter.

[0021] The detection tube marking of this invention uses a transparent, pressure-resistant tube encased in a polytetrafluoroethylene (PTFE) detection tube, forming a pressure-resistant cavity. This allows for the use of a capillary detection tube with a smaller inner diameter and higher mass transfer resistance in high-pressure environments. It can be directly connected to a high-pressure gas source without the need for manual sample injection after depressurization. The entire detection process allows for precise sample injection, avoiding the problem of insufficient sample absorption leading to a short marking length. Furthermore, because the pressure-resistant cavity balances the pressure at both ends of the detection tube, the inner diameter of the detection tube in this invention is on the micrometer scale. Therefore, for the same amount of indicator carrier, the filling length is longer, resulting in a longer color change length and a shorter, clearer color change interface for the same amount of analyte.

[0022] In addition, this invention uses automatic sample introduction and machine vision to automatically determine the color change interface of the detection tube and correlates it with the injection volume. The concentration of the analyte is calculated through chemometrics. Compared with traditional detection tubes that judge the color change length by scale, this is more accurate. The on-site detection conditions have less impact on the measurement accuracy and repeatability, and solve the problem of poor accuracy of detection tube calibration due to factors such as temperature, pressure and manual operation.

[0023] In one specific embodiment, the color sensor employs a laser emitter and a laser receiver, and is configured to be movable. For example, the color sensor can be mounted on a manual slide, a pneumatic slide, or an electric slide, thereby allowing adjustment of the sensing length position of the color sensor.

[0024] In one specific embodiment, the inner diameter of the detection tube is 900μm to 2000μm, preferably 1500μm, and the length is 35cm to 105cm, preferably 100cm.

[0025] The invention uses a detection tube with an inner diameter of micrometers, which makes the color-changing interface narrower and clearer.

[0026] In one specific embodiment, the total length of the filler material of the indicator carrier is 30cm to 100cm, preferably 90cm.

[0027] In one specific embodiment, the detection tube is a polytetrafluoroethylene (PTFE) detection tube.

[0028] In one specific embodiment, the detection tube has a spiral tube structure or a wavy structure.

[0029] Thirdly, the present invention also provides a calibration method based on the above-mentioned natural gas detection pipe analysis and tracing calibration device, comprising the following steps:

[0030] (1) Connect the sample gas source to the calibration device;

[0031] (2) The sample gas source enters the pressure-resistant chamber through the bypass pipe, so that the pressure in the pressure-resistant chamber is consistent with the pressure of the natural gas sample source;

[0032] (3) Open the three-way valve to the direction of the injection line, open the first vent valve, use the sample gas source to flush the injection line, and close the first vent valve. At this time, the pressure inside and outside the detection tube and the left and right ends are all balanced.

[0033] (4) Open the pressure reducing valve, adjust the pressure in the pressure-resistant chamber, adjust the injection flow rate to the preset value, and use the pressure difference between the left and right ends of the detection tube to allow natural gas to enter the detection tube. Turn on the color sensor and flow meter to start the injection.

[0034] (5) The analyte reacts with the indicator carrier in the detection tube, causing the detection tube to change color. When the color change reaches the sensing position of the color sensor, the color sensor sends a signal, the flow meter control valve is turned off, and the flow rate of the flow meter is recorded, which is the inlet volume of the gas source of the sample to be tested. The concentration of the analyte is measured by the ratio of the color change length of the detection tube to the total length of the detection tube and the inlet volume.

[0035] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0036] 1. The present invention provides a natural gas detection tube analysis and traceability calibration device and method, which adopts a chemical metric method for an indicator that reacts with the analyte to perform a color change reaction, and uses pressure-stabilized and flow-stabilized injection and color change identification associated flow metering technology to calibrate and trace the detection tube. The detection tube has high detection accuracy, and no standard gas is required for calibration during measurement. This avoids the problem of large uncertainty in calibration and traceability using standard gas, as well as the problem of poor accuracy of existing detection tube calibration due to factors such as temperature, pressure and manual operation.

[0037] 2. The natural gas detection tube analysis and traceability calibration device provided in this embodiment of the invention uses a detection tube with an inner diameter of micrometers, which enables the discoloration interface to be narrower and clearer;

[0038] 3. The natural gas detection tube analysis and traceability calibration device provided in this embodiment of the invention uses a transparent pressure-resistant tube to cover a polytetrafluoroethylene detection tube, forming a pressure-resistant cavity between the two. This solves the problem that existing detection tubes are not pressure-resistant and are easily broken, and enables capillary detection tubes with larger mass transfer resistance and smaller inner diameters to be used in high-pressure environments. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of the detection tube structure provided in an embodiment of the present invention;

[0041] Figure 2 This is a schematic diagram of the analysis and tracing calibration device provided in an embodiment of the present invention;

[0042] Figure 3 Other shape structures of the detection tube provided in the embodiments of the present invention are shown in the schematic diagram.

[0043] Figure 4 Other shape structures of the detection tube provided in the embodiments of the present invention are shown in the schematic diagram.

[0044] Figure 5 This is a schematic diagram of a traditional detection tube measuring device.

[0045] Component names and markings in the attached diagram:

[0046] 1-Three-way valve, 2-First vent valve, 3-Detection tube, 4-Pressure reducing valve, 5-Transparent pressure-resistant tube, 6-Flow meter, 7-Second vent valve, 8-Stop valve, 9-Color sensor, 10-Pressure-resistant chamber. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0048] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known materials or methods have not been specifically described in order to avoid obscuring the invention.

[0049] Throughout this specification, references to "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the invention. Therefore, the phrases "an embodiment," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. Moreover, those skilled in the art will understand that the illustrations provided herein are for illustrative purposes and are not necessarily drawn to scale. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0050] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0051] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0052] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0053] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0054] Example 1

[0055] like Figures 1-4 As shown, the present invention provides a method for calibrating and tracing the source of natural gas detection pipes, comprising the following steps:

[0056] (1) Mix the quantitative m (mol) detection tube indicator that can react with the target analyte in natural gas with the carrier;

[0057] (2) Divide the carrier containing the indicator into n equal parts and fill them into n detection tubes of the same size. The indicator in each detection tube is m / n (mol), the stoichiometric coefficient of the indicator of the target component in the natural gas is k, and the amount of the target component in the natural gas consumed by the complete reaction with the indicator is km / n (mol).

[0058] (3) When using the analytical tracing calibration device to determine the concentration of the target analyte in natural gas, the ratio r of the discoloration length in the detection tube to the total length of the carrier filling the detection tube corresponds to the molar amount of the target analyte, which is rkm / n(mol).

[0059] (4) By measuring the natural gas injection volume v (L), the concentration of the component to be tested rkm / nv (mol / L) can be detected, thus realizing the calibration and traceability of the detection tube.

[0060] Secondly, the present invention provides a natural gas detection tube analysis and traceability calibration device for implementing the above-mentioned calibration method.

[0061] Includes a pressure testing tube, a color sensor 9, and a flow meter 6;

[0062] The pressure-resistant detection tube body includes a transparent pressure-resistant tube 5 and a detection tube 3 coaxially installed inside the transparent pressure-resistant tube. There is a gap between the outer wall of the detection tube and the inner wall of the transparent pressure-resistant tube to form a pressure-resistant cavity 10. The detection tube is filled with an indicator carrier of the target component to be tested in natural gas.

[0063] A color sensor is provided on the external indicator carrier section of the pressure resistance detection tube; the color sensor is electrically connected to the flow meter, which is located at the end outlet of the pressure resistance detection tube.

[0064] In one specific embodiment, the system further includes a sample injection system, which includes a three-way valve 1. One end of the three-way valve is used to connect to a sample gas source; the second end is used to connect to the front end of a detection tube through a sample injection pipeline; and the third end is connected between the end of the pressure-resistant detection tube and a flow meter through a bypass pipeline, and is connected to the pressure-resistant cavity.

[0065] A first vent valve 2 is installed on the sample injection line;

[0066] The bypass pipeline is equipped with a second vent valve 7 and a shut-off valve 8.

[0067] In one specific embodiment, a pressure regulating device is also included, which includes a pressure reducing valve 4 connected between the end of the pressure-resistant detection tube and the flow meter.

[0068] The detection tube marking of this invention uses a transparent, pressure-resistant tube encased in a polytetrafluoroethylene (PTFE) detection tube, forming a pressure-resistant cavity. This allows for the use of a capillary detection tube with a smaller inner diameter and higher mass transfer resistance in high-pressure environments. It can be directly connected to a high-pressure gas source without the need for manual sample injection after depressurization. The entire detection process allows for precise sample injection, avoiding the problem of insufficient sample absorption leading to a short marking length. Furthermore, because the pressure-resistant cavity balances the pressure at both ends of the detection tube, the inner diameter of the detection tube in this invention is on the micrometer scale. Therefore, for the same amount of indicator carrier, the filling length is longer, resulting in a longer color change length and a shorter, clearer color change interface for the same amount of analyte.

[0069] In addition, this invention uses automatic sample introduction and machine vision to automatically determine the color change interface of the detection tube and correlates it with the injection volume. The concentration of the analyte is calculated through chemometrics. Compared with traditional detection tubes that judge the color change length by scale, this is more accurate. The on-site detection conditions have less impact on the measurement accuracy and repeatability, and solve the problem of poor accuracy of detection tube calibration due to factors such as temperature, pressure and manual operation.

[0070] In one specific embodiment, the color sensor employs a laser emitter and a laser receiver, and is configured to be movable. For example, the color sensor can be mounted on a manual slide, a pneumatic slide, or an electric slide, thereby allowing adjustment of the sensing length position of the color sensor.

[0071] In one specific embodiment, the detection tube has an inner diameter of 1500 μm and a length of 100 cm.

[0072] The invention uses a detection tube with an inner diameter of micrometers, which makes the color-changing interface narrower and clearer.

[0073] In one specific embodiment, the total length of the filler material in the indicator carrier is 90 cm.

[0074] In one specific embodiment, the detection tube is a polytetrafluoroethylene (PTFE) detection tube.

[0075] In one specific embodiment, the detection tube has a spiral tube structure or a wavy structure.

[0076] Thirdly, the present invention also provides a calibration method based on the above-mentioned natural gas detection pipe analysis and tracing calibration device, comprising the following steps:

[0077] (1) Connect the sample gas source to the calibration device;

[0078] (2) The sample gas source enters the pressure-resistant chamber through the bypass pipe, so that the pressure in the pressure-resistant chamber is consistent with the pressure of the natural gas sample source;

[0079] (3) Open the three-way valve to the direction of the injection line, open the first vent valve, use the sample gas source to flush the injection line, and close the first vent valve. At this time, the pressure inside and outside the detection tube and the left and right ends are all balanced.

[0080] (4) Open the pressure reducing valve, adjust the pressure in the pressure-resistant chamber, adjust the injection flow rate to the preset value, and use the pressure difference between the left and right ends of the detection tube to allow natural gas to enter the detection tube. Turn on the color sensor and flow meter to start the injection.

[0081] (5) The analyte reacts with the indicator carrier in the detection tube, causing the detection tube to change color. When the color change reaches the sensing position of the color sensor, the color sensor sends a signal, the flow meter control valve is turned off, and the flow rate of the flow meter is recorded, which is the inlet volume of the gas source of the sample to be tested. The concentration of the analyte is measured by the ratio of the color change length of the detection tube to the total length of the detection tube and the inlet volume.

[0082] Example 2

[0083] This invention provides an analytical traceability calibration device and method for a detection tube used to detect hydrogen sulfide concentration in natural gas, comprising a sample injection system, a pressure-resistant detection tube body, a color sensor, a pressure reducing valve, and a flow meter. The pressure-resistant detection tube body is a self-made quartz detection tube installed inside a transparent pressure-resistant tube, with a gap between the outer wall of the detection tube and the transparent pressure-resistant tube. The quartz tube contains six capillaries with equal and uniformly distributed inner diameters, separated by a quartz glass body. Each capillary has an inner diameter of 1000 micrometers, and the total length of the quartz tube is 105 cm, with each capillary being 100 cm long. The interior of the capillaries is coated with a silanized coating and filled with HgCl2-impregnated silica gel with a particle size of 10 micrometers.

[0084] The HgCl2-impregnated silica gel carrier was screened five times using a 12500-mesh (1-micron) filter. After pretreatment including acid washing, water washing, and organic solvent soaking, a quantitative amount of 2.71 g (m = 0.01 mol) of HgCl2 was added to 1500 g of carrier. After thorough mixing and drying, the carrier containing the indicator was evenly divided into several portions (n ​​≈ 564653) and filled into several (564653) detection tubes of the same size. Therefore, each detection tube contained 1.77 × 10⁻⁶ indicators. -8 When HgCl2 reacts with H2S in natural gas, the stoichiometric coefficient k is 1. The amount of hydrogen sulfide consumed in the natural gas to fully react with the indicator is km / n mol. If the color change detection point is set in the exact center of the detection tube, the ratio r of the color change length to the total length of the detection tube is 0.5, and the corresponding H2S content is 0.885 × 10⁻⁶. -8 mol. When the color-changing length of the detection tube reaches the color-changing recognition point (i.e., the setting position of the color sensor), the natural gas injection volume v (L) is measured, and the concentration of the analyte can be obtained as 0.885 × 10⁻⁶ mol. -8 / v(mol / L). This invention uses a chemometric method, which directly measures the accurate concentration of the analyte by measuring the molar mass of the indicator and then by the color change length and the natural gas intake. It eliminates the need for calibration with gaseous standard substances and is not affected by ambient temperature, pressure, or manual operation.

[0085] Samples were taken from the pressure gauge interface of the external pipeline of a condensate gas field processing plant for analysis. In order to compare the measurement results with the differences of existing measurement methods, the mercury content was determined by the present invention and GB / T 16781.1-2017 "Determination of Mercury Content in Natural Gas Part 1: Iodine Chemisorption Sampling Method" in the same time period.

[0086] The detection method of this invention involves setting a color sensor at the starting point of the detection tube (10cm). At this point, the color change length of the detection tube is 20cm (the position of the color sensor can be adjusted according to actual conditions to ensure sufficient natural gas is injected while minimizing the time it takes for the color change to reach the sensor). The corresponding mercury content consumed in the reaction is 2.21 × 10⁻⁶. -9 mol. Connect to a natural gas sample source (6.2 MPa), such as... Figure 2 As shown, open the three-way valve 1 and the second vent valve 7 to purge the sample inlet line bypass, close the second vent valve 7, and slowly open the shut-off valve 8. Natural gas enters the pressure-resistant chamber of the detection tube from the right end. After filling, switch the three-way valve sample inlet line so that both ends of the detection tube are under natural gas source pressure, thus achieving pressure balance. At this time, natural gas will not enter the detection tube. Then, slowly open the first vent valve 2 to purge the sample inlet line, close the first vent valve 2, open the pressure regulating device, and adjust the pressure reducing valve to allow the detection... There is a pressure difference between the left and right ends of the tube. Natural gas enters from the left end of the detection tube and flows out through the pressure reducing valve. The injection flow rate is adjusted to 1000 ml / min. Six repeated tests are conducted using the same batch of detection tubes. After turning on the color sensor and flow meter, the injection begins. The flow meter valve automatically closes after approximately 20 minutes, and the flow rate is recorded. The flow rates for the six tests are 20.113 L, 22.011 L, 19.423 L, 18.546 L, 24.042 L, and 21.951 L, respectively. The mercury content consumed in the reaction corresponding to the color change of the 10 cm detection tube is 2.21 × 10⁻⁶. -9 The mercury content in the natural gas measured in six measurements was 22040.5 ng / m³, with a mass of approximately 443.3 ng. 3 20139.9ng / m 3 22823.5ng / m 3 23902.7ng / m 3 18438.6ng / m 3 20195.0ng / m 3 The average value was 21256.7 ng / m 3 The measurement repeatability (RSD) was 9.5%.

[0087] Example 2

[0088] This invention provides a method for calibration using the natural gas analysis and traceability calibration device of the embodiment, as follows: The color sensor is positioned at the midpoint (50cm) of the detection tube, at which point the color change length of the detection tube is 50cm. A silanized pipeline is connected to the natural gas sample source (3.2MPa). The three-way valve and the second vent valve are opened to purge the bypass of the injection pipeline. The second vent valve 7 is closed, and the pressure reducing valve 4 is slowly opened. Natural gas enters the pressure-resistant chamber of the detection tube from the right end, filling the injection pipeline of the switching three-way valve. Both ends of the detection tube are under natural gas source pressure, thus achieving pressure balance. Then, the first vent valve 2 is slowly opened to purge the injection pipeline. The first vent valve 2 is closed, the pressure and flow stabilization system is turned on, and the pressure valve is adjusted to create a pressure difference between the left and right ends of the detection tube. Natural gas enters from the left end of the detection tube and flows out through the pressure reducing valve. The injection flow rate is adjusted to 10ml / min. The color sensor and flow meter are turned on, and the injection begins. After approximately 7 minutes, the flow meter valve automatically closes, and the flow rate is recorded as 60.50ml. The above test was repeated five times using the same batch of test tubes, and the recorded flow rates were 60.15 ml, 60.32 ml, 60.56 ml, 60.73 ml, and 60.95 ml, respectively. The hydrogen sulfide mass concentration in the natural gas was c = 0.885 × 10⁻⁶. -8 ×34.08×10 3 / v×10 -6 =301.608 / v (mg / m³) 3 Therefore, the hydrogen sulfide content in the natural gas produced by the purification plant was 4.96 mg / m³ in six separate measurements. 3 ), 4.99 (mg / m 3 ), 4.97 (mg / m 3 ), 4.96 (mg / m 3 ), 4.94 (mg / m 3 ), 4.92 (mg / m 3 The average value was 4.96 (mg / m³). 3 The volume fraction was 3.30 ppm, and the measurement repeatability (RSD) was 0.47%.

[0089] For comparison, the method of calibrating the detection tube using a gaseous standard reference involves using a bottle of hydrogen sulfide gaseous standard reference (6 ppm, relative expanded uncertainty of 2%, k=2) in the laboratory, with the same experimental apparatus and the same batch of detection tubes of the same model, under the same experimental parameters. The recorded flow rate is 33.10 ml. The hydrogen sulfide content measured in the above six measurements were 3.28 ppm, 3.30 ppm, 3.29 ppm, 3.28 ppm, 3.27 ppm, and 3.26 ppm, respectively, with an average value of 3.28 ppm. It is evident that the measurement results obtained by this patented method are almost identical to those obtained by calibration using a gaseous standard reference reference.

[0090] Comparative Example 1

[0091] This comparative example provides a method for detecting and analyzing hydrogen sulfide using a conventional detection tube. The steps are as follows: Based on GB / T11060.11-2014 "Determination of Sulfur Compounds in Natural Gas - Part 11: Determination of Hydrogen Sulfide Content by Colored Length Detection Tube Method", a Guangming Beichuan AP-20CT manual sampling pump and a Guangming Beichuan 120U detection tube (0.1-6.0 ppm) are used. Figure 5 As shown, samples were taken and analyzed at the pressure gauge interface of the external pipeline of the same natural gas purification plant. A 50ml sample was manually and slowly drawn, and the length of the discoloration of the test tube, changing from pale yellow to peach, was observed to be approximately 2.1 ppm. The same batch of test tubes was used to repeat the above test five times, with readings of 2.6 ppm, 1.6 ppm, 2.3 ppm, 1.7 ppm, and 3.0 ppm. The atmospheric pressure during measurement was 98.6 kPa, and the temperature was 21.3℃. According to the test tube's instruction manual, the measured value = reading × 2 × 101.325 kPa / atmospheric pressure at the measurement point × temperature correction factor. The temperature correction factor for 21.3℃ was found to be 1.0. Therefore, the calculated values ​​for the six measurements were 4.32 ppm, 5.34 ppm, 3.29 ppm, 4.73 ppm, 3.49 ppm, and 6.17 ppm, with an average value of 4.55 ppm. The measurement repeatability (RSD) was 24%.

[0092] Comparative Example 2

[0093] This comparative example provides a method for determining hydrogen sulfide content using iodometric titration, as follows: According to GB / T11060.1-2023 Determination of Sulfur Compounds in Natural Gas Part 1: Determination of Hydrogen Sulfide Content by Iodometric Titration, the original sampling and calculation data and results are as follows: A hydrogen sulfide sampling absorber is connected to the pressure gauge interface of the external pipeline of the same natural gas purification plant. 50 mL of zinc acetate solution is added to the absorber. A rubber bulb is used to gently agitate the absorber inlet to allow some solution to enter the space below the glass orifice plate. All parts are tightly connected using a short rubber tubing section. The screw clamp is fully opened, and the sampling valve is slowly opened, allowing the gas to be analyzed to fully displace the gas in the sampling conduit through the vent pipe. The flow meter reading is recorded as the initial sampling reading. The screw clamp is adjusted to allow the gas to pass through the absorber at a flow rate of 430 mL / min. The sampling volumes for two parallel tests are 150.000 L and 153.000 L, respectively. The gas temperature is recorded as 27.0℃ and the atmospheric pressure as 98.60 kPa. Remove the absorber, add 10 mL (or 20 mL) of iodine solution (2.5 g / L) using a pipette, then add 10 mL of hydrochloric acid solution. Attach the absorber head and gently agitate the solution at the absorber inlet with a bulb syringe to ensure thorough mixing. After reacting for 3 minutes, transfer the solution to a 250 mL iodine flask and titrate with sodium thiosulfate standard solution (0.01006 mol / L). Perform a blank test following the same procedure. The titrant volumes used in the two tests were 3.0 mL and 3.05 mL, respectively. The calculated hydrogen sulfide concentrations for the two tests were 3.73 mg / L. 3 and 3.67 mg / m 3 The average value was 3.70 mg / m³. 3 This translates to a volume fraction of 2.62 ppm.

[0094] Comparing the three measurement methods in Example 2 and Comparative Examples 1 and 2, it can be seen that the hydrogen sulfide measurement result using the method of the present invention is 3.30 ppm, with a deviation of 0.68 ppm from the result determined by the iodometric method (2.62 ppm). The hydrogen sulfide measurement value using the traditional detection tube method is 4.55 ppm, with a deviation of 1.93 ppm from the result determined by the iodometric method (2.62 ppm). It is evident that the measurement accuracy of the present invention is significantly improved compared to the traditional detection tube method (at the 2.62 ppm measurement point, the deviation has been reduced from 1.93 ppm to 0.68 ppm). Regarding measurement precision, the RSD of six repeated measurements using the present invention is 0.47%, compared to the RSD of 24% for six repeated measurements using the traditional detection tube method, representing an improvement in repeatability of approximately 51 times.

[0095] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for calibrating and tracing the source of natural gas detection pipes, characterized in that, Includes the following steps: (1) Mix the quantitative m (mol) detection tube indicator that can react with the target analyte in natural gas with the carrier; (2) Divide the carrier containing the indicator into n equal parts and fill them into n detection tubes of the same size. The indicator in each detection tube is m / n (mol), the stoichiometric coefficient of the indicator of the target component in the natural gas is k, and the amount of the target component in the natural gas consumed by the complete reaction with the indicator is km / n (mol). (3) When using the analytical tracing calibration device to determine the concentration of the target analyte in natural gas, the ratio r of the discoloration length in the detection tube to the total length of the carrier filling the detection tube corresponds to the molar amount of the target analyte, which is rkm / n(mol). (4) By measuring the natural gas injection volume v (L), the concentration of the component to be tested rkm / nv (mol / L) can be detected, thus realizing the calibration and traceability of the detection tube.

2. A natural gas detection tube analysis and traceability calibration device for implementing the calibration method of claim 1, characterized in that, Includes a pressure testing tube, a color sensor, and a flow meter; The pressure-resistant detection tube body includes a transparent pressure-resistant tube and a detection tube coaxially installed inside the transparent pressure-resistant tube. There is a gap between the outer wall of the detection tube and the inner wall of the transparent pressure-resistant tube to form a pressure-resistant cavity. The detection tube is filled with an indicator carrier of the target component to be tested in natural gas. A color sensor is provided on the external indicator carrier section of the pressure resistance detection tube; the color sensor is electrically connected to the flow meter, which is located at the end outlet of the pressure resistance detection tube.

3. The natural gas detection pipe analysis and traceability calibration device according to claim 2, characterized in that, It also includes a sample injection system, which includes a three-way valve. One end of the three-way valve is used to connect to the sample gas source; the second end is used to connect to the front end of the detection tube through the sample injection pipeline; and the third end is connected between the end of the pressure-resistant detection tube and the flow meter through a bypass pipeline, and is connected to the pressure-resistant cavity. A first vent valve is installed on the sample inlet line; The bypass pipeline is equipped with a second vent valve and a shut-off valve.

4. The natural gas detection pipe analysis and traceability calibration device according to claim 3, characterized in that, It also includes a pressure regulating device, which includes a pressure reducing valve connected between the end of the pressure-resistant detection tube and the flow meter.

5. The natural gas detection pipe analysis and traceability calibration device according to claim 2, characterized in that, The inner diameter of the detection tube is 900μm to 2000μm, and the length is 35cm to 105cm.

6. The natural gas detection tube analysis and traceability calibration device according to claim 2, characterized in that, The total length of the filler material in the indicator carrier is 30cm to 100cm.

7. The natural gas detection pipe analysis and traceability calibration device according to claim 2, characterized in that, The detection tube is a polytetrafluoroethylene (PTFE) detection tube.

8. The natural gas detection pipe analysis and traceability calibration device according to claim 2, characterized in that, The detection tube has a spiral tube structure or a wavy structure.

9. A calibration method for the natural gas detection tube analysis and traceability calibration device according to any one of claims 2 to 8, characterized in that, Includes the following steps: (1) Connect the sample gas source to the calibration device; (2) The sample gas source enters the pressure-resistant chamber through the bypass pipe, so that the pressure in the pressure-resistant chamber is consistent with the pressure of the natural gas sample source; (3) Open the three-way valve to the direction of the injection line, open the first vent valve, use the sample gas source to flush the injection line, and close the first vent valve. At this time, the pressure inside and outside the detection tube and the left and right ends are all balanced. (4) Open the pressure reducing valve, adjust the pressure in the pressure-resistant chamber, adjust the injection flow rate to the preset value, and use the pressure difference between the left and right ends of the detection tube to allow natural gas to enter the detection tube. Turn on the color sensor and flow meter to start the injection. (5) The analyte reacts with the indicator carrier in the detection tube, causing the detection tube to change color. When the color change reaches the sensing position of the color sensor, the color sensor sends a signal, the flow meter control valve is turned off, and the flow rate of the flow meter is recorded, which is the inlet volume of the gas source of the sample to be tested. The concentration of the analyte is measured by the ratio of the color change length of the detection tube to the total length of the detection tube and the inlet volume.

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